Although thunderclap headache (TCH) is rare, it can indicate the presence of a serious underlying disorder and thus warrants immediate medical attention. Defined as a severe, explosive headache reaching peak intensity within 1 minute of onset and often lacking any apparent trigger, TCH can be idiopathic and ultimately determined to be benign, or may result from vascular problems, injury, or structural abnormalities.1
“This is such an intense experience that patients usually go to the emergency room” to seek help, said Robert Cowan, MD, FAAN, professor of neurology and chief of the division of headache medicine at Stanford University. “The big question is whether this is a primary headache or a secondary headache due to subarachnoid hemorrhage” or another serious condition, he told Neurology Advisor.
Many of the potential causes of TCH are highlighted below.
-Rapid reductions in blood flow to the brain due to events such as head injury or aneurysm may cause severe, sudden headaches. Accompanying symptoms may include numbness, weakness, and speech or vision problems, which require urgent assessment. Another potential cause of TCH is arterial dissection, which may result from injury such as a fall, or after exertion as in weightlifting, or may have no identifiable cause.1
-Hemorrhagic stroke, ischemic stroke, and subarachnoid hemorrhage (SAH) can cause also TCH. SAH has been observed in up to 25% of TCH patients.2 “A person who develops a severe headache with sexual activity or orgasm can also have a bleed, aneurysm, or dissection,” wrote Deborah Tepper, MD, in a 2016 paper published in Headache: The Journal of Head and Face Pain.1 “If headaches occur repeatedly with sexual activity over a long period, this problem is much less likely to be dangerous.”
-Mild-to-moderate head injury may lead to TCH hours or days following the event, due to an epidural hemorrhage, subdural hematoma, or central venous thrombosis. “This is why people, even those who have already been to the emergency department, had a CT, and had normal neurological examinations, need to be re-evaluated immediately if they develop a new or worse headache, or any new weakness, decreased awareness, speech problems, or unusual symptoms in the days following an injury,” according to Dr Tepper.1
-Reversible cerebral vasoconstriction syndrome (RCVS) is increasingly recognized as a common cause of recurrent TCH attacks. In many cases, RCVS is accompanied by transient changes in vision, sensation, strength, or consciousness. There are numerous potential causes of RCVS, including stimulant use and oral contraceptives.1
Unlike benign causes of TCH, RCVS has been “linked with clinical (focal neurological deficits and seizure) and radiological (cortical SAH, intracranial hemorrhage, ischemic stroke, arterial dissection and posterior reversible encephalopathy syndrome) abnormalities, and sometimes increased morbidity and mortality,” as noted in a 2014 study described in the Journal of Headache and Pain.1 The results of this investigation showed a diagnosis of RCVS in 45.8% of patients with TCH, while primary headache and secondary causes were diagnosed in 45.8% and 8.3% of TCH patients.
Diagnosis of RCVS typically requires immediate magnetic resonance angiography (MRA) or CT angiogram (CTA), as the blood vessels may appear normal after the spasm has resolved.1 “Systemic examination of cerebral vessels should be adopted in these patients, so that they may benefit from potential treatments such as avoidance of triggers and use of nimodipine,” wrote the authors of the 2014 study.2
-Vasculitis can lead to a sudden headache with a slightly longer onset than typically occurs with TCH but may present with the sudden visual and neurological impairments. Unilateral headache or pain behind the eye or with chewing in patients >50 years warrant prompt evaluation, as these are signs of giant cell arteritis, the most common form of vasculitis.1 If the physical exam leads to suspicion of giant cell arteritis (GCA), then a temporal artery biopsy may be performed.3 GCA can be treated with corticosteroids, and lack of treatment can lead to permanent vision loss.
-Sudden onset of headaches in pregnancy, especially in late pregnancy, may indicate the presence of various disorders including eclampsia and pituitary apoplexy.1
TCH may be the only early warning sign of vascular changes or brain injury. “Clues that this is a dangerous headache include any neurological changes such as weakness, visual changes, trouble thinking, or unusual sensations,” Dr Tepper stated.1 CT and spinal tap or lumbar puncture may aid in diagnosis if performed shortly after onset, while MRA or CTA may prove useful in the later stages.
However, Dr Cowan notes that “the answer to this is almost always in the history more than any imaging or spinal tap. Sometimes you need to do those things, but usually a careful history and exam will give you the answer before you have to start throwing money at it.”
If no cause is identified after thorough evaluation, a diagnosis of primary TCH – which is thought to be benign – may be appropriate. “There really isn’t a treatment for primary TCH – these headaches are of such a short duration that they’re over before anything can be done,” said Dr Cowan.
“If a patient experiences these headaches frequently, sometimes an anti-inflammatory is prescribed for prevention,” he added. For headaches with predictable triggers – such as sexual activity – treatment with an indomethacin can be helpful.1 A daily preventive medication, such as an antihypertensive, may be needed for more frequent headaches.
“Any thunderclap headache accompanied by fever, weakness, loss of vision or sensation, or accompanied by confusion or changes in speech or thinking, needs immediate evaluation,” Dr Tepper emphasized.1 “The possible problems that can result in thunderclap headache are many, and the consequences can be … severe.”
1. Tepper D. Thunderclap headaches. Headache. 2016;56:1563-1564.
2. Cheng YC, Kuo KH, Lai TH. A common cause of sudden and thunderclap headaches: reversible cerebral vasoconstriction syndrome. J Headache Pain. 2014;15(1):13.
3. Arthritis Foundation. Giant cell arteritis. https://www.arthritis.org/about-arthritis/types/giant-cell-arteritis/ Accessed on March 5, 2019.